function cdot = ex72(t, c)
% 
% this file defines the equation set (7.2.19), (7.2.20), (7.2.27)
% and (7.2.28) with x1=c(2), CA=c(1)
%

cdot(1) = -c(2);
cdot(2) = -100.*c(2) -200.0*c(1);
cdot(3) = -c(4);
cdot(4) = -200.*c(3) - 100.*c(4);
cdot = cdot(:);
